feat(mcp): add package-backed ast-grep MCP

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

packages/ast-grep-mcp/src/index.ts

@@ -0,0 +1,4 @@
+export { handleAstGrepMcpRequest, runMcpStdioServer } from "./mcp";
+export type { AstGrepMcpOptions, JsonRpcId, JsonRpcResponse, JsonRpcResult, McpToolDescriptor, TextContent } from "./mcp";
+export { runSg } from "./runner";
+export type { RunOptions } from "./runner";